Special livery aircraft just for fun. There used to be a lot more jetting around (737s and 757s) but as they go in for their major checks with repainting (C-checks??) they are being painted/stripped/decaled back to the AA standard livery. AA doesn't have the money right now to keep up the practice.

Anyway, it's not like AA's current and very long-lived livery is much less retro. I think it has been with AA for approximately 35 years. It certainly has aged well, too, in my opinion.